Battery life of portable audio devices may be improved by shutting down the audio amplifier of the portable device when the portable device is not in use, and waking up the audio amplifier only as it is needed. However, if a fast turn-on time is used to turn on the audio amplifier from full shutdown, pop-and-click noise may be caused by the fast turn on.
One solution to this problem is to put the audio device into a sleep/standby or mute mode instead of a full shutdown mode. However, this solution may require extra current to keep all of the major nodes of the device charged. This means that the audio device still consumes extra battery power even though it is not being used. Power consumption in the standby mode becomes significant compared to the power consumption in the active mode if the device remains in standby much longer than it is active, which is typically the case for most portable audio devices.